Printed circuit construction



Feb. 26, 19.52 w, H MYERS 2,586,854

PRINTED CIRCUIT CONSTRUCTION Filed April 19, 1947 2 SHEETS-SHEET l F IG. I

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lo? los |07 FIG |05 los 85 Feb- 25, 1952 w. H. MYERS 2,586,854

PRINTED CIRCUIT CONSTRUCTION Filed April 19, 1947 2 SHEETS- SHEET 2 INVENTOR ATTORN EY Patented Feb. 26, 1952 PRINTED CIRCUIT ooNsraUc'rloN 'William H. Myers, Fort Wayne, Ind., assigner, by mesne assignments, to Farnsworth vResearch Corporation, Aa corporation of 'Indiana Application April 19, 1947, Serial No. 742,655

(C1. Z50-I6) 4 Claims.

'Ihis invention relates to printed electric circuits and particularly relates to a novel laminated plate having disposed thereon conductors and circuit components and arranged to provide elec trostatic and electromagnetic shielding between groups of the circuit components.

The input circuit of an electron discharge device, such as an amplier, usually must be shielded electrostatically and electromagnetically from the output circuit of the amplifier. This is effected in a conventional radio receiver by spacially separating the circuit components forming the input circuit from those forming the output circuit.

Recently so-called printed circuits have been proposed for special applications where space is at a premium such, for example, as for hearing aids. A printed circuit conventionally comprises a dielectric plate having printed on or bonded to both its surfaces electric conductors in the form of conducting paths and circuit components such as resistors and condenser-s. It has, for example, been suggested to arrange a circuit for coupling two amplifier stages on the two surfaces of a dielectric plate. These printed circuits have been used heretofore with special miniature tubes.

However, in view of the fact that the circuit components provided on the two surfaces of a dielectric plate are not electrostatically and electromagnetically shielded from each other, it has not been possible heretofore to arrange the entire input and output circuit of an electron discharge device such as an amplifier on one such plate. Printed circuits of this type greatly reduce the number of soldered connections required in any given circuit because the circuit components provided on the plate may be connected by conductors in the form of conducting paths which are directly printed on or bonded to the surface of the plate. It would, accordingly, be desirable to arrange these printed circuits in such a manner that standard vacuum tubes may be mounted thereon and that connections may be made selectively from the prong of a tube socket to the circuit components on either one of the two surfaces of the plate. In that case it would be possible to utilize printed circuits in the construction of conventional radio receivers with a large saving in labor due to the reduced number of soldered connections which normal-v ly must be provided between the circuit components.

It is an object of the present invention, therefore, to provide a novel laminated plate bearing printed conductors and circuit elements and having means for electrostatically and electromagnetically shielding the circuit components on one of the wsurfaces of the laminated plate from those on the reverse surface of the plate.

Another object of the invention is to provide a laminated plate for a printed circuit having apertures extending therethrough and contact elements in the apertures for connecting circuit components on one of the surfaces of the plate either to circuit components on the opposite surface of the plate or to an electrostatic shield provided in the center of the laminated plate.

A further object of the invention is to provide a laminated plate for a printed circuit having apertures therein for mounting the prongs of standard vacuum tubes or of transformers and the like circuit components which cannot be printed or otherwise provided on the surfaces of the laminated plate.

In accordance with the present invention there is provideda first and a second dielectric member and a conductive layer disposed between the two members. Circuit components are provided on the outer surfaces of the two members.

The conductive layer which is preferably connected to ground accordingly forms an electrostatic shield between the circuit components on the outer surfaces of the two members. Preferably the circuit components disposed on the outer surface of one of the dielectric members form the input circuit of an electron discharge device, while the circuit components on the outer surface of the other dielectric member form the output circuit of the electron discharge device.

For a better understanding of the invention, together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawings', and its scope will be pointed out in the appended claims.

In the accompanying drawings:

Fig. l is a circuit diagram of an amplifier;

Fig. 2 is a plan view of a vacuum tube socket and its prongs;

Fig. 3 is an exploded perspective View of a laminated plate embodying the present invention and bearing a printed circuit corresponding to the circuit of Fig. 1;

Fig. 4 is a view in perspective with parts broken away of the laminated plate of Fig. 3 mounted on a chassis;

Fig. 5 is a cross sectional View taken on lines 5-5 of Fig. 4, and illustrates a connection between a conductor on the top surface of the laminated plate and the grounded electrostatic shield thereof;

Fig. 6 is a cross sectional view taken on lines 6-6 of Fig. 4, and shows a connection from thecenter of a printed coil provided on the top surface of the laminated plate to the bottom surface of the plate and back to the output conductor of the coll;

Fig. '7 is a cross sectional view taken on line '1 -1 of Fig. 4, and illustrates a fragmentary portion of a transformer and a contact element for connecting one pin of the transformer to a conductor on the laminated plate;

Fig. 8 is a view in perspective of a conventional tunable transformer and its pins; and

Fig. 9 is a cross sectional view taken on 'line 9-9 of Fig. 4, and shows contact elements for connecting the prong of a tube to conductors'on the outer surfaces of the laminated plate.

Referring now to Fig. 1 of the drawings, there is illustrated, by way oi' example, a conventional amplifier circuit which may be printed or otherwise provided on a laminated plate in accordance with the present invention. The amplifier circuit of Fig. 1 may be used, for instance, as the intermediate-frequency 'amplifier stage of a superheterodyne radio receiver and includes pentode I which may be of the 6SK7 type. Pentode l0 comprises cathode II, control grid I2, screen grid I3, suppressor grid I4 and anode or plate I5. Cathode II may be indirectly heated by filament vII having one lead II connected to ground as shown, and another lead I8 connected to the heater supply as indicated at H.

The input signal is impressed upon input lead connected to control grid I2 through peaking coil 2l and coupling condenser 22 arranged in series. Peaking coil 2| is provided for improving the high frequency response of the amplifier. Control grid I2 is connected to ground through grid leak resistor 23. Cathode I' I is connected to ground through a biasing network 'including cathode resistor 24 by-passed by condenser 25. Screen grid I3 is connected to a suitable anode voltage supply indicated at B+ through lead 26 and a suitable screen grid resistor 21 which is by'- passed to ground by condenser 28. Suppressor grid I4 is connected to ground through lead 30.

Anode I 5 is also connected to the anode voltage supply B+ through anode resistor 3i which'is by-passed to ground by condenser 32. In the anode circuit there is provided a tuned circuit including fixed condenser 33 and inductance element 34 which may be tunable by permeability tuning as is conventional. Inductance element 34 forms the primary of a transformer, the secondary of which is formed by inductance element 35 which may also be permeability ltuned and which is by-passed by a fixed condenser 36. The output signal is obtained from output lead 31,

While the opposite terminal of inductance element 35 is grounded. y

It is to be understood that the circuit of Fig. 1 has merely been shown by way of example, in order to describe more clearly the printed circuit which may be provided on the laminated plate in accordance with this invention.

Referring now to Fig. 2, there is illustrated a plan View of tube socket 45 of a 6SK7 type pentode such as shown at Iii in Fig. l. The tube is provided with eight lprongs 4I, 42, 43, 44, 45, 46, 4-'I and 48. Prongs 4I to 48 connect respectively to the shell, one terminal of the filament, the suppressor grid, the vcontrol grid, the cathode, the screen grid, the other 'terminal of the filament and the plate of tube I9 as indicated.

Referring now to Fig. 3, there is shown an of a sheet of metal, but it is preferred to apply metallic layer 53 by spraying the metal on one oi' the adiacent surfaces of plates 5I, 52. A1- though metallic layer 53 will ordinarily be bonded to at least one of the adjacent surfaces of sheets 5I and 52, it has been shown for convenience in Fig. 3 as being separated from both plates 5I and 52. Metallic layer 53 electrostatically shields the circuit components provided on the outer surface of plate 5I from those disposed on the outer surface of plate 52. If metallic layer 53 is of a suitable thickness which depends upon the frequency of the signal, it may also serve as an electromagnetic shield between the outer surfaces of plates 5I and 52. Preferably metallic layer 53 is connected to ground `through wire 102 which may have one terminal soldered or otherwise connected to layer 53 and its other terminal grounded as shown.

Thus, in accordance with the present invention it is feasible to provide the input circuit of an electron discharge device such as amplifier I0 on of example in Fig. 1 have been shown applied to laminated plate 50.

The input signal is impressed upon input lead or wire 2U which is connected by soldering or in 1 any other suitable way to printed coil 54 corresponding to peaking coil 2I. printed coil 54 may consist of a conducting path in the shape of a helix which may be applied to dielectric plate 5I by printing or spraying, forv example, silver oxide through a suitable stencil or template onto the surface of plate 5I. The silver oxide is then burned on plate 5I to provide a silver coating on the plate, in accordance with conventional methods. It is also feasible to utilize a silk screening process which is another conventional method.

At the center point of coil 54 there is provided aperture 55 which extends through plate 5I, metallic layer 53 and plate 52 as indicated. On the outer surface of plate 52 there is provided a conductor 56 which extends from aperture 55 to aperture 51 which also passes through the three layers of laminated plate 50. In a manner to be described hereinafter a connection is made by,

transfer conductors through apertures 55 and 51 for connecting the center point of coil 54 withy conductor or conducting path 58 provided on plate 5I. Conductors 56 and 58 are bonded to the surface of plates 53 and 5I in the same manner as is coil 54.

Conductor 58 is connected with condenser 66 corresponding to coupling condenser 22 in Fig. 1. The other terminal of condenser 60 is connected to conductor 6I. Condenser 60 may be provided in a conventional manner on plate 5I and may consist of a conducting layer bonded to plate 5I which is covered by a dielectric circular sheet which in turn is provided on its outer surface with another conductive layer.

Laminated plate 50 is provided with eight apertures indicated at 62, 63, 64, 65, 66, 61, 68 and 69 which have been labeled on the three sheets 5I, 53 and 52 with consecutive numerals from 1 to 8. Apertures 62 to 69 are arranged to receive prongsL 4I to 48 of tube socket 40 illustrated in Fig. 2.

Thus, conductor 6I extends to aperture 65 which will receive prongs 44 (Fig. 2) for connection to the control grid I2 ,oftube IB. A

Resistor I0 is also connected to conductor BI As shown in Fig. 3,

and corresponds to grid leak resistor 23. Resistor may be bonded to the surface of dielectric plate 5| by applying thereto carbon mixed with a suitable binder as is conventional. The other terminal of resistor 18 is connected to conductor 1| which in turn leads to aperture 12 extending through laminated plate 50. `By means of aperture 12 conductor 1| may be connected to yground by a `transfer conductor in a manner to be explained hereinafter.

Conductor 1| leads to aperture 66 through re.- sistor 13 corresponding to cathode resistor 24. Aperture 66 is adapted to receive prong 45-w`hich is connected to cathode I I of tube I0. Resistor 13 is by-passed by condenser 14 correspondingfto bypass condenser 25 so that resistor 13 and condenser 14 form a biasing network. Condenser v1,6 is connected between conductor 1| and conductor 19 leading to aperture 61 which is adapted to receive `prong 46 connected to screen `grid I3 of tube I8. Condenser 16 `accordingly corresponds tocondenser 28. Conductor 11 connects lead or wire 18 to the heater supply H and extends to aperture 68 which is arranged for receiving-prong 41 connected to one terminalof the filament of the tube. Thus, conductor 11 and wire 18 correspond to lead I8 in Fig. 1.

Conductor 88 `extends between apertures 6,2, 63 and 64 for a 'purpose to be explained hereinafter. Apertures 62, 63 and 64 are adapted to receive respectively prongs 4I, 42 and 43 connecting to ythe shell, one terminal of the `filament and the suppressor grid vwhich are all grounded.

The output circuit of tube ID is provided on the outer-surface of dielectric plate 52. The output circuit includes an intermediate-frequency transformer corresponding to inductance elements 34 and 35. The transformer may be Har.- ranged in a suitable housing 82 as illustrated in Fig. 8 which is provided with four pins 83. By means of screws 84 the position of each of the two cores with respect to its associated coilfmay be varied thereby to effect permeability tuning of the transformer.

For receiving the fourpins 83 of transformer 82, there are provided -four apertures 85, 86, 81 and 88 through laminated plate 50. Between apertures 85 and 59 there is provided conductor 90. Aperture 69 is arranged for receiving prong 48 which is connected to -plate I5 of tube I0. Condenser 9| is arranged between conductors 99 and 92 which latter in turn leads to aperture 86. Condenser 9| corresponds to condenser 33. It is to be understood that an inductance element corresponding to coil 34 willbe provided between apertures 85 and 86 when transformer housing 82 is inserted into apertures 85 to 88. Conductor 92 is connected through resistor 93 corresponding to anode resistor 3| with the anode voltage supply indicated at B-I- through wire 94 and conductor `89. Resistor 95 is connected to wire 94 through conductor 89. The other terminal of resistor 95 is connected to conductor 99 extending to aperture 61 which will receive prong 46 connected to screen grid |3. Resistor 95 accordingly corresponds to screen grid resistor 21.

Between apertures 81 and 88 an inductance element corresponding to coil 35 will be connected which is by-passed by condenser 96 corresponding to condenser 36 in Fig. 1. Output lead or wire 91 is connected to condenser 96 through a conductor leading to aperture 81 and corresponds to output lead v31, while the other terminal of condenser 96 is connected to ground through conductor'98 .extending to aperture 88 ina-manner 6 to be described hereinafter. Condenser |00 corresponds to condenser 32 and is connected between conductor 98, that is ground, and the junction point of condenser 9| and resistor 93. Conductor 98 leads to aperture I0| extending through laminated sheet 50.

It will be understood that various connections between the outer surfaces of plates 5I, 52 and metallic layer 53 may be effected through the apertures extending through laminated plate 56. As illustrated, for example, in Fig. 5, aperture 12 may receive a transfer conductor arranged for connecting conductor 1I to metallic layer 53 thereby to ground conductor 1| through wire |62 connected to ground as shown in Fig. 3. To this end a metallic sleeve may be extended from metallic layer 53 or may be electrically connected thereto. Contact element or transfer conductor |96 is arranged to be pushed through aperture 12, and its head portion |91 will make contact with conductor 1| while its shank contacts sleeve |85. Spring clip |89 retains transfer conductor |66 as illustrated.

Fig. 6` is a cross sectional view through coil 54 and apertures 55 and 51. Transfer conductors |66 are provided in apertures 55 and 51. Thus, head |91 of the contact element in aperture 55 makes contact with coil 54 on plate 5|, and its spring clip |98 contacts conductor 55 on bottom plate 52. Transfer conductor |86 vin aperture 51 connects conductor 56 on plate 52 to conductor 58 on plate 5i as illustrated. It will be observed that metallic layer 53 is spaced about transfer conductors |66 so that transfer conductors |96 cannot make electrical contact with metallic layer 53. As shown in Fig. 3, apertures 55 and 51and metallic layer 53 are larger than those in plates 5| and 52. On the other hand, apertures 12 and IDI in metallic layer 53 are smaller than apertures 5,5 and 51.

By means of the transfer connection illustrated in Fig. 6 itis feasible to avoid Crossovers between circuit elements or conductors. This is accomplished by simply connecting a circuit element or conductor to a conductor on the opposite plate and then making a return connection to the rst plate at a suitable distance from the rst connection.

In Fig. '1 there is shown a fragmentary portion of transformer' housing 82 which has one of its ins 83 inserted into aperture 85 for making contact with conductor 98. To this end there is provided contact element ||0 which consists of a hollow sleeve having la head portion Iii which contacts conductor 96. Contact sleeve H9 is slotted as shown at |I2 to provide yielding projections for insuring electrical contact between contact sleeve i i@ and the pin on transformer S2. It will be observed again `that aperture 85 in metallic layer 53 is larger than those in plates 5| and 52 to prevent electrical Contact between metallic layer 53 and contact sleeve Elfi.

It is to be understood that suitable contact sleeves such as illustrated at I I8 in Fig. 7 may be provided in apertures 62 to 69 lfor inserting herein prongs il to 48 of the tube. The transfer conductors which may be provided in apertures 62 to 64 in plate 5| are interconnected by conductor 86 on plate 5| to insure prop-er connection to ground of prongs 4| to 53. However, if each prong 4I to 43 is separately connected to ground, conductor 85 is superfluous may be omitted.

As shown inFig. y9, electrical contact may be established .betweena .Conductor on ula-tei! 0h52 and one of the prongs 4| to 48 of tube socket 49 by means of contact elements liti. Fig. 9 illustrates a sectional view through aperture El adapted to receive prong 46 which connects to the screen grid of the tube. Accordingly, prong 46 should be electrically connected to conductors 'I9 and 99 which are connected in turn to condenser I6 and resistor 95. Contact element 129 having a central aperture may be suitably secured to conductor 19 and dielectric plate 5l by soldering or cementing and has a spring clip l2| for providing electrical contact with prong 46 extending through aperture 6'! and contact element |26. Another Contact element 122 is electrically connected to conductor 99 and may be identical to element 120. Thus, by inserting prong 46 through aperture 61, electrical connection is established between conductors 19 and 99 and prong 16. It is to be understood that the other prongs of the tube may be connected to their respective conductors in a similar manner.

Referring now to Fig. 4, there is illustrated laminated sheet 56 comprising dielectric plates 5I, 52 and metallic layer 53 mounted on a suitable chassis frame IlEi. Laminated plate 59 may be secured to chassis frame l l5 by suitable means such as screws l lli. The height of chassis frame H5 may be such that tubes, transformers and thelike component parts of the circuit may be arranged therein.

Preferably laminated plate 59 is provided with an insulating varnish shown at I il which may applied by spraying or by dipping laminated plate 50 into the varnish. Thus, all exposed conductors, resistors and condensers are covered by the insulating varnish. It is furthermore to be understood that several laminated plates such as shown at 50 may be superposed or stacked for providing thereon a plurality of printed circuits.

It will be seen that by means of the laminated plate 50 of the present invention even complicated circuits may be provided on one laminated plate with a, resulting saving of a large number of soldered connections. Those circuit components such as tubes, transformers, ganged condensers and the like may be inserted into the laminated plates through suitable apertures which are preferably molded when the dielectric plates are manufactured. It is also feasible to mold dielectric plates 5l and 52 with 11p-turned edge portions in 'Y the shape of chassis frame I l5 so that the entire laminated plate is self -supporting While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modiiications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A first and a second dielectric member, a conductive layer extending substantially between the entire adjacent surfaces of said members, a first series of circuit components including conductors forming substantially an input circuit of an electron discharge device and disposed on the outer surface of said first member, and a second series of circuit components including conductors forming substantially an output circuit of the electron discharge device and disposed on the outer surface of said second member, said conductive 1ayer providing an electrostatic shield between said input and output circuits of said electron discharge device.

2. A rst and a second dielectric member, a metallic 1ayer extending substantially between the entire adjacent surfaces of said members, a first series of circuit components including conductors forming substantially an input circuit of an electron discharge device and disposed on the outer surface of said first member, a second series of circuit components including conductors forming substantially an output circuit of the electron discharge device and disposed on the outer surface of said second member, a source of fixed potential, and means for connecting said source to said metallic layer, whereby said metallic layer electrostatically shields said input circuit from said output circuit. y

3. A first and a second dielectric member, a metallic layer extending substantially between the entire adjacent surfaces of said members and forming an electrostatic shield, circuit components including conductors and impedance elements disposed on the outer surfaces of each of said members, means for holding said members and said layer together to form a unitary struc- Y ture, terminals for the connection of electron discharge devices connected to said conductors, a layer of insulating material covering substantially said structure, said structure being provided with an aperture extending therethrough, and means insulated from said metallic layer disposed in said aperture for electrically connecting a conductor on said rst member to a conductor on said second member.

4. A first and a second dielectric member,a metallic layer extending substantially between the entire adjacent surfaces of said members and forming an electrostatic shield, a source of fixed potential, means for connecting said source to said metallic 1ayer, circuit components including conductors and impedance elements bonded to the outer surfaces of each of said members, terminals for the connection of electron discharge devices connected to said conductors, means for holding said members and said layer together to form a unitary structure, said structure being provided with an aperture extending therethrough, and means insulated from said metallic layer disposed in said aperture for electrically connecting a conductor on one of said members to said metallic layer.

WILLIAM H. MYERS.

REFERENCES CITED The following references are of record inthe le of this patent:

UNITED STATES PATENTS Great Britain Aug. 25, 1936 OTHER REFERENCES Scientific American: August 1946, an article, Electronics, by John Markus; pages 63 to 65.

- Electronic Industries: April 1946, an article on Printed Circuit Wiring, pages 90, 91 and 122. 

